Alkylation of aromatic hydrocarbons with isoparaffins



Sept. 29, 1953 F. E. coNDoN ALKYLATION OF AROMATIC HYDROCARBONS WITH ISOPARAFFINS Filed Aug. 30)"1946 HBZINVLGECI NVENTOR. F E CONDON III Y ATTORNEYS Patented Sept. 29,1953

ALKYLATION OF AROMATIC "HYDROCAR- BONS WITH ISOPARAFFINS Francis E. Condon, Bartlesville, Okla., assigner to Phillips Petroleum Company, a corporation of Delaware Application Aug-ust 30, 1946 vSerial No. 694,131

7 Claims.. 1

The present linvention relates to a method of accomplishing the alkylation of `aromatic hydrocarbons with isoparailins, i.' e. the introduction on a ring carbon atom of an alkyl group derived from and having the structure of an isoparafln.

The alkylated aromatic hydrocarbons are of great commercial importance. They .are especially valuable for blending in motor and ,aviation gasoline and as solvents ,and chemical intermediates. Previously they have been made predominantly or exclusively by the alkylation of the aromatic hydrocarbon with an aliphatic olefin or an alkyl halide .or lan aliphatic alcohol.

The principal object of the present invention is to provide a method for the alkylation of aromatic hydrocarbons with isoparamns. Another object is to provide an improved method of making alkylbenzenes, especially tertiary alkyl benzenes, for example, tertiary butyl benzene.

Another object is to make available a process for the alkylation of aromatic hydrocarbons with isobutane as a tertiary butylating agent. Numerous other objects will more fully hereinafter appear.

The accompanying drawing portrays .diagrammatically one arrangement of equipment and now which may be employed for carrying out the present invention in one typical embodiment thereof.

I have now discovered that aromatic hydrocarbons can be alkylated with isoparains by subjecting a mixture of the aromatic hydrocarbon, an isoparaiin, 4an aliphatic oleiin and an alkylation catalyst to reaction conditions such that the aromatic hydrocarbon is alkylated with the olefin. My invention is based on the discovery that when such a process is conducted, concomitant alkylation of the aromatic hydrocarbon With an alkyl group .derived from and having the structure of the soparain is accomplished.

The temperature at which the reaction is conducted is preferably substantially atmospheric. Moderate temperatures ranging from 20 to 30 C. are very suitable for carrying out the present invention and are preferred. However, 'temperatures ranging from C. to as high as 50 C. .may be employed.

The time of reaction should be Sufficient to bring the reaction substantially to equilibrium. Usually the reaction time will be at least 5 minutes and not over 1 hour. Reaction times of the order of 5 to 15 minutes are often adequate. The time should be as short as possible in order t0 give maximum output from equipment of a given size.

Any suitable liquid alkylation catalyst which is capable of effecting alkylation of the aromatic with the olen under conditions herein described may be employed Generally speaking, I employ the liquid inorganic acids which have been used heretofore for alkylatimgisoparalins with aliphatic .oleflns These acids are substantially anhydrous hydroluoric `acid and concentrated sulfuric acid. .Hydrofluoric acid is by far preferred for `the practice of .my invention.

The alkylation yields not only the alkyl benzenes formed by alkylation of the aromatic with the olefin but lalso alkyl benzenes wherein the alkyl substituent is derived vfrom and has .the structure of the isoparanin employed.

The term isoparaiiin is used herein with its usual meaning, i. e, to denote any branched chain oaraiiin hydrocarbon. This term has been heretofore used in atleast two different wayaknamely to denote (11) the 2-methyl alkanes; `for example isobutane .2-rnethy1 propane), sopentane r(2- methyl butano). ischexane (2V-methyl permane) and ,so on through the paraiiin series and (2") the branched chain p araflins generally. I use it in the second sense. -In addition to these two meanings the term isooctane has had an additional meaning since it has been employed to designate the specific branched chain octane 2,2,fl-trimethyl pentane. The number of carbon atoms per molecule inthe isoparaiiin may range from 4 upwardly to any desired number, say i0 or even 20 .or higher. Generally the isoparaiiin will not have more than .8 carbon atoms per molecule, More commonly the isoparainn will be isobutano or isopentane since these are readily available and `since the corresponding alkyl benzenes are more in demand under present conditions.

It should be pointed out, however, that the term isopentane is used herein Withits usual meaning, i. e. to denote 2-methyl butane.

The pressure maintained in the reaction zone should be such as to hold all of the ingredients present in the reaction zone in the liquid phase.

The amount of catalyst employed may vary within fairly wide limits. Preferably it will be at least equal to the amount of hydrocarbon or organic phase present in the reaction zone. In general the ratio of Acatalyst to hydrocarbon charge should be Afrom 2:1 to 1:2 by volume. A ratio of about 1:1 will commonly be employed.

The concentration of aromatic hydrocarbon in the hydrocarbon feed to the reaction zone is preferably less than 10 percent by weight and more preferably not over 2 per cent by weight.

The concentration of olen in the hydrocarbon charge preferably ranges from 0.5 to 2 molecular equivalents per molecular equivalent of aromatic hydrocarbon present.

'The molecular ratio of isoparaiiin to aromatic hydrocarbon in the yreaction zone is generally 3 between 10 and 1000. A ratio of at least 50 is preferred.

Any alkylatable aromatic hydrocarbon may be employed in the practice of my invention. Generally I prefer to use the monocyclic aromatics such as benzene, toluene, xylene, ethylbenzene, isopropyl benzene, etc. However, I may use the polycyclic aromatics such as naphthalene.

The reaction zone should be equipped with means for agitating the contents thereof vigorously so as to produce the desired intimacy of contact between the immiscible catalyst phase and the hydrocarbon phase. The reaction zone should also be provided with means for maintaining the proper temperature therein. Any suitable contacting equipment may be used, such as that commonly employed for carrying out the alkylation of isoparafiins with aliphatic olefins at moderate temperatures and pressure.

Generally speaking, the reaction conditions are such that the predominant reaction is alkylation of the aromatic hydrocarbon with the olefin to produce the corresponding alkylated aromatic and that an important though lesser reaction is the concomitant alkylation of the aromatic with an alkyl group corresponding to and derived from the isoparaihn.

In accordance with this invention, a mixture comprising an isoparaiiin to be used as alkylating agent, for example, isobutane if tertiary butylation is desired, an aromatic hydrocarbon to be alkylated, for example, benzene, and an aliphatic olefin (preferably one having a different number of carbon atoms than the isoparaiiin to be used as alkylating agent), for example, propylene, is subjected to the action of an alkylating catalyst, which may suitably be hydrofluoric acid, at a convenient temperature which need not diier appreciably from ordinary room temperature (25 C.) and for a suitable period of time which may conveniently be of the order of 5 to 15 minutes. Operation may suitably be continuous with recycling of the catalyst.

The catalyst-free eiuent is then freed of unchanged isoparaiiin (which must, for the most successful operation of this process, be present in large excess), suitably by distillation.

The alkylation product will contain alkyl benzenes derived from alkylation of the benzene with the olefin used, i. e. those alkyl benzenes that would be obtained in the absence of isoparaflin. But also, there will be present an appreciable amount of alkyl benzenes derived from and therefore having an alkyl group with the structure of the isoparain used. For example, a considerable amount of tertiary butyl benzene will be found in the alkylate from an isobutane-benzene-propylene mixture. The yield of aromatic alkylation product derived from isoparafn will be greater, the greater is the ratio of isoparafn to aromatic hydrocarbon in the feed. Thus, a preferred method of operating consists in using less than per cent by weight of aromatic hydrocarbon in the charge mixture. The percentage yield of aromatic alkylation product derived from the isoparaffin will be increased still further, however, as the percentage of aromatic hydrocarbon in the feed is decreased, so that a concentration of 2 per cent by weight or aromatic hydrocarbon is better than a concentration of l0 per cent by weight. Lower concentrations result in an even greater percentage of aromatic alkylate derived from the isoparain, but the penalty of having to free the effluent from a greater amount of unchanged isoparafiin becomes greater. Generally, the concentration of olefin in the charge is maintained approximately molecularly equivalent to the amount of aromatic hydrocarbon, although varying this from 0.5 molecular equivalent to 2 molecular equivalents of olen per molecular equivalent of aromatic should not have any adverse effect on the percentage of aromatic alkylate derived from the isoparafn. Thus, the use of feeds in which the molecular ratio of isoparain to aromatic hydrocarbon is between 10 and 1000 and preferably is at least 50, and the molecular ratio of aromatic hydrocarbon to olenic hydrocarbon is between 0.5 and 2.0, for the purpose of obtaining alkyl benzenes derived from the isoparafiin, is within the scope of the present invention.

While the preceding discussion, and the examples, refer speciiically to a mixture of isobutane, benzene and propylene, in which case the alkyl benzenes derived from the isoparafiin consist of tertiary butyl benzene, di-(tertiary butyl) benzene and tertiary butyl isopropyl benzenes, the use of other mixtures of an analogous nature is not beyond the scope of the present invention. The use of isopentane, for example, instead of isobutane, when the production of tertiary amyl benzenes is desired, is an obvious variation of the present process. The use of olens other than propylene, for example, the use of butylenes when isopentane is the paraflin used, is an entirely feasible variation of the present process. Preferably, however, the olefin used has a number of carbon atoms different from that of the isoparaflin used, in order to facilitate separation, by fractional distillation, of the alkyl benzenes derived from the olen from those derived from the isoparaiiin.

The process of the present invention is conducted under substantially anhydrous conditions i. e. in the presence of not more than a trace of water. This may be accomplished by using commercially available anhydrous hydrofluoric acid, by dehydrating the hydrocarbon feeds in the usual way and by taking ordinary precautions to exclude water from access to the reaction zone as by using conventional closed pressure-resisting contacter and subsequent pieces of equipment.

In the discussion and in the examples, hydrofluoric acid is used as the catalyst for bringing about aromatic alkylation by soparaflins. However, it will be obvious to one skilled in the art that other alkylating catalysts may produce the same result. For example, concentrated sulfuric acid, aluminum chloride, or various modified forms of aluminum chloride, which are generally known to be useful alkylating catalysts, may be used instead of hydrofluoric acid for the production of alkylbenzenes derived from isoparaiiins in mixtures of isoparafns, olens, and aromatic hydrocarbons. However' 1 prefer to use substantially anhydrous hydroiluoric acid.

In all applications, however, the use of a high molecular ratio of isopara-fn to aromatic hydrocarbon, i. e. at least 10:1 and preferably at least 50:1, in order to increase the percentage of alkylated aromatic hydrocarbons derived from the isoparaflin, is to be considered an Optimus modus operandi, and a principle which is herewith disclosed for the rst time.

A second novel principle herewith disclosed for the iirst time, is the necessity of an olefin (or its chemical equivalent) in order to bring about aromatic alkylation by an isoparaflin under the mild conditions of temperature and contact time .5 used in the present process. Thus itis well known that isobutane in the absence of olefins will not alkylate benzene under the mild conditions here specified as preferable: namely, (1) the use of hydroiiuoric acid as a catalyst; (2) a temperature near 25 C.; (3) a contact time of 5 to 15 minutes. The function of the olefin may be to remove hydrogen from the isoparafiin, thus converting it to an olen, which then alkylates the aromatic hydrocarbon. A corresponding amount of olefin would then be expected to be hydrogenated to its corresponding paraiiin hydrocarbon. y

Since, in the presence of hydrfiuoric acid, alkyl fluorides exhibit the same chemical behavior as their parent oleiins in many alkylation reactions, it is to be expected that an alkyl iiuoride may function as well as an oleiin to bring about aromatic alkylation by an isoparainn in a mixture of alkyl fluoride, isoparaiiin, and aromatic hydrocarbon with hydroiiuoric acid as a catalyst. Similarly, if an 'aluminum chloride catalyst is used, an alkyl chloride would be eX- pected to function as well as its parent olefin in promoting aromatic alkylation by an isoparafn. Therefore the alkyl halides are believed to be substantial equivalents of aliphatic oleiins for the practice of the present invention. However, in general, I prefer to employ the clehns rather than the alkyl halides.

amples Two runs are described in which blends of iso butane, benzene and propylene were pumped into a 1470 ml. copper-plated steel reactor Where they were intimately mixed with substantially anhydrous hydrcfluoric acid. The acid-hydrocarbon emulsion so produced passed to a settler, from which substantially hydrocarbon-free acid was recycled to the reactor, and substantially acid-free hydrocarbon was collected in a large' receiver. In the reactor, the acid-to-hydrocarbon ratio was maintained near unity, by addition of small amounts of fresh acid when necessary. The reactor was surrounded by a stirred water bath for maintenance of temperature. The effluent hydrocarbon was Washed with Water to remove traces of acid, and the excess isobutane was removed in a i-foot corrosion-resistant metal fractionating column 1 1/4 inches in diameter packed with 1/4-inoh Raschig rings. Butane-free alkylate was analyzed by fractional distillation in glass columns. The pertinent data are presented in the table.

TABLE Example Example l 2 `(-o'rn'Iia'rison of the data of Examples 1 and 2 shows that a iive-fold increase in the mole-ratio of isobutane to benzene served to more than double the percentage of tertiary-butylbenzene inthe butano-xfree alkylate.

In the drawing, isobutane, propylene, benzene and HF `in suitable proportions are fed to re'- actor I vialines 2; 3, 4 and 5, respectively.- These materials may of course be admixecl prior to introduction to reactor I. The reaction effluent passes via line 6 to settler 'I where it separates into an acid phase and a hydrocarbon phase. The acid phase may be recycled in part or in toto to vessel I by means of line 8. If desired, a suitable portion of the acidphase may be withdrawn from the recycle circuit. The withdrawn acid phase may be passed to a suitable recovery or rerunsystem in amount such as to keep activity of the acid catalyst in the system at the proper level and to keep impurities therein from building up to an objectionable level. The hydrocarbon phase may be passed via line 9 to unit I0 wherein HF is removed in any suitable way. The hydrocarbon stream is then fed via line II to debutanizer I2 which removes the unreacted isobutane and any normal lontane overhead. This overhead may be recycled to reactor 2 Via line I3'. If desired a suitable portion may be withdrawn from the system as indicated. Propane may be removed in admixture with the vbiitane at this point or may have been removed admixture with HF in unit I0. If desired unit IIJ may be eliminated and the free HF may be removed overhead in column I2 in admixture with propane and butanes, the resulting fraction being recycled in Whole or in part to reactor 2 via line I3. The bottoms fraction from column I2 is fed via line I4 to fractionation system I5 wherein it is resolved into any desired fractions, as a fraction of tertiary butylbenzene removed via line I6. Other fractions such as isoparafins above iso'- butane, benzene, isopropyibenzene, etc. may be recoveredby means of the system I5.

From the foregoing description it will be seen that the present invention makes possible a hitherto unknown reaction, namely the alkylation of aromatic hydrocarbons with an isoparaflin' to give an alkylated aromatic wherein the alkyl gro-up is derived from and corresponds to said isoparaflin. This is highly advantageous and so far as I am aware has not heretofore been thought possibile. Another advantage is that the reaction takes place under moderate conditions of temperature and pressure and can be carriedout in equipment which is readily available. Another advantage is that the process affords a simple and economical way of making alkylated aromatic hydrocarbons wherein the alkyl group substituent on the nuclear carbon atom or atoms is derived from an isoparafiin.

Iclai-m:

1. The process of alkylating an aromatic hydrocarbon which comprises subjecting a hydrocarbon mixture in which the reactive coniponents consist essentially of an aromatic hydrocarbon, an isoparaiifin having ly to 20 carbon atoms per molecule and an aliphatic olefin, having askeletal configuration diierent from that of the isoparaflin, in admixture with an alkyla.- tion catalyst consisting of substantially anhydrous hydrofluoric acid, the molecular ratioof said isoparain to said aromatic hydrocarbon being' at least 10:1, the molecular ratio of said aromatic hydrocarbon to said olefin being between 0.5 :"1 and 210:1 to a reaction temperature of from 7 20 to 30 C. for a reaction time of at leastl 5 minutes but not over one hour and under a pressure such as to maintain the materials present in the liquid phase, whereby said aromatic hydrocarbon is alkylated with said olefin and is concomitantly alkylated with an alkyl group derived from and having the skeletal structure of said isoparain and recovering said aromatic hydrocarbon alkylated with said alkyl group derived from and having the skeletal structure of said isoparain as the product of the process.

2. The process of alkylating an aromatic hydrocarbon which comprises subjecting a hydrocarbon mixture in which the reactive components consist essentially of an aromatic hydrocarbon, an isoparain having 4 to 20 carbon atoms per molecule and an aliphatic olefin, having a skeletal configuration different from that of the isoparain, in admixture with an alkylation catalyst consisting essentially of anhydrous hydrofiuoric acid, the molecular ratio of said isoparafn to said aromatic hydrocarbon being at least 50:1, the molecular ratio of said aromatic hydrocarbon to said olefin being between 0.5:1 and 2.0:l, to a temperature of from 20 to 30 C. for a reaction time of at least 5 minutes but not over 15 minutes, whereby said aromatic hydrocarbon is alkylated with said olefin and is concomitantly alkylated with an alkyl group derived from and having the skeletal structure of said isoparaiiin and recovering said aromatic hydrocarbon alkylated with said alkyl group derived from and having the skeletal structure of said isoparaffin as the product of the process.

3. The process of alkylating benzene with isobutane which comprises subjecting a hydrocarbon mixture in which the reactive components consist essentially of benzene, isobutane and an aliphatic olefin having a different number of carbon atoms per molecule from isobutane in admixture with an alkylation catalyst consisting of substantially anhydrous hydrouoric acid to a reaction temperature of from 20 to 30 C. for a period of time of at least 5 minutes and not over one hour, the molecular ratio of said isobutane to said benzene being at least :1 but not greater than 100011, the molecular ratio of said benzene to said olefin being between 0.5:1 and 2.0:1 the reaction pressure being such as to hold the components in the liquid phase, whereby said benzene is alkylated with a tertiary butyl group derived from said isobutane concomitantly with the alkylation of said benzene with said olefin and recovering said benzene alkylated with a tertbutyl group as a product of the process.

4. The process of alkylating benzene with isobutane which comprises subjecting a hydrocarbcn mixture in which the reactive components consist essentially of benzene, isobutane and propylene in admixture with an alkylation catalyst consisting essentially of anhydrous hydrofluoric acid, the molecular ratio of said isobutane to said benzene being at least 50:1 and the molecular ratio of said benzene to said propylene being between 0.511 and 2.0:1, to a reaction temperature of from 20 to 30 C. for a reaction time of from 5 to 15 minutes under a pressure sulficient to hold the components in liquid phase and thereby effecting alkylation of said benzene with a tertiary butyl group derived from said isobutane concomitantly with alkylation of said benzene with said propylene and recovering said benzene alkylated with a tert-butyl group as a product of the process.

5. The process of alkylating benzene with isobutaneto give tertiary butyl benzene which comprises subjecting a hydrocarbon mixture in which the reactive components consist of benzene, isobutane and propylene in admixture with an alkylation catalyst consisting of substantially anhydrous hydrofluoric acid, the molecular ratio of said isobutane to said benzene being approximately 63.6:1 and the molecular ratio of said benzene to said propylene being approximately 1:1, the acid-hydrocarbon ratio being maintained at approximately unity, to a temperature of approximately 92 F'. for a contact time of approximately 6.7 minutes and a pressure of approximately pounds per square inch gauge while subjecting the mixture to agitation to produce intimate contact between the acid and the hydrocarbon phases, and thereby effecting simultaneous alkylation of said benzene with a tertiary butyl group derived from said isobutane and alkylation of said benzene with said propylene, withdrawing the resulting mixture and causing same to separate into an acid phase and a hydrocarbon phase, and recovering tertiary butyl benzene from said hydrocarbon phase.

6. The process of alkylating an aromatic hydrocarbon which comprises subjecting a hydrocarbon mixture in which the reactive components comprise an aromatic hydrocarbon, an isoparaihn having 4 to 2O carbon atoms per molecule and an aliphatic olefin, having a skeletal configuration different from that of the isoparafn, in admixture with an alkylation catalyst comprising hydroiiuoric acid, the molecular ratio of said isoparaflin to said aromatic hydrocarbon being at least 10:1, the molecular ratio of said aromatic hydrocarbon to said olefin being between 0.5 :1 and 2.0:1, to a reaction temperature in the range between 0 and 50 C. for a reaction time of at least ve minutes but not over one hour and under a pressure such as to maintain a liquid phase, whereby said aromatic hydrocarbon is alkylated with said olefin and is concomitantly alkylated with an alkyl group derived from and having the skeletal structure of isoparailin and recovering said aromatic hydrocarbon alkylated with an alkyl group derived from and having the skeletal structure of said isoparaii'in as a product of the process.

'7. The process of alkylating an aromatic hydrocarbon which comprises subjecting a hydrocarbon mixture in which the reactive components consist essentially of an aromatic hydrocarbon, an isoparaiiin having 4 to 20 carbon atoms per molecule and an aliphatic olefin, having a skeletal configuration different from that of the isoparain, in adrnixture with an alkylation catalyst consisting essentially of anhydrous hydrouoric acid, the molecular ratio of said isoparain to said aromatic hydrocarbon being at least 50:1, the molecular ratio of said aromatic hydrocarbon to said olefin being between 0.5:1 and 20:1, to a temperature of from 0 to 50 C. for a reaction time of at least 5 minutes but not over 15 minutes, whereby said aromatic hydrocarbon is alkylated with said olefin and is concomitantly alkylated with an alkyl group derived from and having the skeletal structure of said isoparaifin and recovering said aromatic hydrocarbon alkylated with an alkyl group derived from having the skeletal structure of said isoparaiiin as a product of the process.

FRANCIS E. CONDON.

(References on following page) 10 References Cited in the le of this patent Number Name Date 2,413,161 Zerner et a1 Dec. 24, 1946 UNITED STATES PATENTS 2,419,692 Shoemaker et a1. Apr. 29, 1947 Number Name Date 2,433,020 Becker Dec. 23, 1947 2,234,984 seehanen et 21. Mar. 1s, 1941 5 2,456,119 Friedman et a1. Dec. 14, 1948 2,275,312 Tinker Mar, 3, 1942 2,456,435 Matuszak Dec. 14, 1948 2,305,026 Munday Dec. 15, 1942 2,456,672 Bloch et a1. Dec. 21, 1948 2,349,211 Tulleners May 16, 1944 2,459,636 Fenney Jan. 18, 1949 2,399,368 Matuszak Apr. 30, 1946 2,408,753 Burk Oct. 8, 1946 10 

1. THE PROCESS OF ALKYLATING AN AROMATIC HYDROCARBON WHICH COMPRISES SUBJECTING A HYDROCARBON MIXTURE IN WHICH THE REACTIVE COMPONENTS CONSISTS ESSENTIALLY OF AN AROMATIC HYDROCARBON, AN ISOPARAFFIN HAVING 4 TO 20 CARBON ATOMS PER MOLECULE AND AN ALIPHATIC OLEFIN, HAVING A SKELETAL CONFIGURATION DIFFERENT FROM THAT OF THE ISOPARAFFIN, IN ADMIXTURE WITH AN ALKYLATION CATALYST CONSISTING OF SUBSTANTIALLY ANHYDROUS HYDROFLUORIC ACID, THE MOLECULAR RATIO OF SAID ISOPARAFFIN TO SAID AROMATIC HYDROCARBON BEING AT LEAST 10:1, THE MOLECULAR RATIO OF SAID AROMATIC HYDROCARBON TO SAID OLEFIN BEING BETWEEN 0.5:1 AND 2.0:1 TO A REACTION TEMPERATURE OF FROM 20 TO 30* C. FOR A REACTION TIME OF AT LEAST 5 MINUTES BUT NOT OVER ONE HOUR AND UNDER A PRESSURE SUCH AS TO MAINTAIN THE MATERIALS PRESENT IN THE LIQUID PHASE, WHEREBY SAID AROMATIC HYDROCARBON IS ALKYLATED WITH SAID OLEFIN AND IS CONCOMITANTLY ALKYLATED WITH AN ALKYL GROUP DERIVED FROM AND HAVING THE SKELETAL STRUCTRUE OF SAID ISOPARAFFIN AND RECOVERING SAID AROMATIC HYDROCARBON ALKYLATED WITH SAID ALKYL GROUP DERIVED FROM AND HAVING THE SKELETAL STRUCTRUE OF SAID ISOPARAFFIN AS THE PRODUCT OF THE PROCESS. 